An example of an electronic combination lock which is self-powered or has self-generated power is U.S. Pat. No. 5,061,923 issued to Miller et. al. The Miller patent discloses a stepper motor as a generator to create the electrical power for the lock.
The Mas-Hamilton Group X-07 Lock, the Mas-Hamilton Group Cencon, and Auditcon Locks, all available from the Mas-Hamilton Group, Lexington, Ky., each have stepper motors driven as generators to provide self-contained powering capability.
Other patents which disclose self-powered dial combination locks incorporating generators include U.S. Pat. No. 5,170,431 to Gerald L. Dawson, et.al.; U.S. Pat. No. 5,410,301 to Gerald L. Dawson, et.al.; U.S. Pat. No. 5,493,279 to Gerald L. Dawson, et.al.; U.S. Pat. No. 5,488,358 to James E. Hamilton, et. al.; and U.S. Pat. No. 5,488,660 to Gerald L. Dawson, et. al., all assigned to Mas-Hamilton Group, Lexington, Ky. U.S. Pat. No. 5,265,452 to Gerald L. Dawson, et. al., discloses a keyed cylinder electronic lock with a self-contained generator.
Generation of electrical power depends on the relative movement of a coil through a magnetic field. The more times a coil or coils are passed through a magnetic field or fields, the greater the power generated for any particular time span.
Due to the limited number of coils and magnetic segments or fields of the armature, the power requirement of a lock such as the X-07 or Cencon dictates a step-up drive in order to derive sufficient rotation and, therefore, power from the stepper motor generator. The stepper motors of the Miller U.S. Pat. No. 5,061,923 patent and the Mas-Hamilton Group locks, identified above, further use the stepper motor output as pulse signals for input and control of the microprocessor in the lock electronics.
The step-up drive required to increase the generator output of the stepper motor requires considerable force and stronger components. The stepped up stepper motor drive requires more moving parts than a direct drive, and may result in an increase of mechanical failures, adversely affecting reliability.
The increased forces required to rotate the dial of a lock having a stepped-up drive result both in a degradation of the dial control as well as an operator perception that the dial is difficult to operate.
In locks wherever combinations and commands are entered through a keyboard, the necessity to securely contain and maintain the combination entry signal source within the lock case, inside the secure container, is eliminated because the generator does not supply the data input signals.
In locks using a generator for data input signals, the generator may be used for power and data. Thus, in those instances, it is desirable to maintain the power generator or stepper motor within the lock casing as it will then be disposed within the secure container as well as within the casing itself which will reduce the ability to electronically detect the signals being generated by the lock during combination entry.